Originally posted by whubbard Q: Does it matter where in the series I put the bulb?Q: So if the bulb gets bright I should stop right away...or will the bulb burn out if something is wrong?

What you will experience with the bulb is a bright glow as the filters in the supply charge up, which will die down to a dimmer glow as the amp settles in. If there is a bias problem or any kind of short, the bulb will glow at a high brightness. Once you connect the speakers any kind of offset or imbalance will cause the bulb to brighten, depending on how much the measurements are off.

Most normal amps will play reasonably loud and cleanly on a 100watt bulb before the bulb glows to brightly and the voltages drop below where it can properly function.

This is a quick and easy way to test for functionality and avoid toasting a rebuilt circuit due to a solder bridge or a missed bad component. Especially if you have a good channel to compare it to.

If all is working well you should be able to rough dial in the bias and offset adjustments with the speaker disconnected, take the amp off of the bulb for the real setup.

The only place you can get into trouble is when there is a stability problem that only shows up when full power is applied to the amp. But dealing with those comes with experience; with the bulb in series you can at least get to that point and it's not the norm.

Enjoy, Mike.

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